Greg Clark is not an instantly recognisable politician. Indeed, the Communities and Local Government Secretary could happily go undetected in most shopping centres and high streets.

Yet if the measure of success in Government is actually making a difference, then Clark must be regarded as one of the more effective cabinet ministers in recent years.

He has driven the devolution agenda in a way that his predecessor Eric Pickles never did.

The Government’s spin machine places the Chancellor at the heart of devolving powers and budgets to our great cities and regions, what with his Northern Powerhouse and Midlands Engine. But Greg Clark was building the engine long before George Osborne hitched a ride.

Back in 2012 it was Mr Clark, then a local government minister, who risked making himself highly unpopular in the Conservative party by backing elected mayors. Clark turned up in Birmingham at a reception (hosted by Chamberlain Files publisher RJF Public Affairs) to mark the result of the mayoral referendum.

Sadly, the party turned into a wake (albeit a jolly one) as the city decisively rejected the notion of a mayor, but Mr Clark was undeterred. Since then he has proved highly effective at pushing the devolution agenda, largely behind the scenes, while leaving Mr Osborne to bask in the glory, such as it is.

This very English revolution, a softly-softly approach to change, is gradually becoming apparent as more and more cities and city regions set up combined authorities under metro mayors. By 2026 areas not under the rule of an elected mayor will be the exception, and all of this will have been achieved by agreement between local and central government rather than imposition.

Mr Clark’s reputation for ‘doing things’ rather than simply accepting a less riskier strategy of embracing the status quo was evident again last week when the Communities Secretary took what may turn out to be one of the pivotal decisions to be made by this Government, and once again he will not be popular among most Tory MPs.

By giving approval for 1,500 houses to be built on green belt land near Gloucester Mr Clark made it more likely that similar developments encroaching into the protected countryside across England will get approval as local councils come under increasing pressure from the Government to solve a housing shortage.

His ruling reversed the position previously taken by ministers, with Mr Clark deciding green belt land could be built on where there is a significant local need for housing – which is almost everywhere. The decision is in stark contrast to current planning laws which state that green belt development should only be permitted “in very special circumstances”.

Mr Clark admitted the decision would be “harmful” to the green belt and lead to the loss of the “essential characteristic of openness”, but he said there would be a substantial benefit from the new homes by addressing undersupply in the area.

The knock-on effect from Mr Clark’s decision is likely to be felt in Birmingham where the city council is involved in a desperate search to identify enough land to address a housing shortfall and build 89,000 new dwellings. There is enough brownfield land in Birmingham itself to build only 51,000 new homes, leaving 38,000 to be built across the city boundary in Worcestershire, Staffordshire and Warwickshire.

Controversially, the council has identified green belt land in Sutton Coldfield for up to 5,000 homes, and up to 1,000 homes in Bromsgrove, with both proposals stirring up hostile local protests.

Greg Clark’s latest intervention will surely make it more rather than less likely that a proportion of Birmingham’s housing need will have to be met through building on green belt land.

The Campaign to Protect Rural England has been quick to latch on to the Communities Secretary’s decision, claiming that it will “open up the floodgates” for further green belt development. CPRE estimates there are proposals already in the pipeline for 35,000 homes in the green belt and has warned that Mr Clark’s decision in Gloucester will make it difficult for local planning authorities to reject further development.

CPRE planning campaign manager Paul Miner claimed Mr Clark’s decision was tantamount to telling developers that green belt protections can be overridden and “this is a route likely to be taken by hard-pressed local authorities.”